Method of making a reconstituted tobacco sheet



United States Patent 3,386,449 METHOD 0F MAKING A RECGNSTHTUTED TOBACQOSHEET John D. Hind, Richmond, Va., assignor to Philip Morris,Incorporated, New York, N.Y., a corporation of Virginia No Drawing.Filed June 16, 1966, Ser. No. 557,927 3 Claims. (6!. 131-140) Thisinvention relates, generally to an improved method for the production ofreconstituted tobacco composition comprising tobacco and tobacco derivedpectins which serve as a binder for the tobacco.

During the production and processing of tobacco products, includingaging, blending, sheet forming, cutting, drying, cooling, screening,shaping and packaging, considerable amounts of tobacco fines and tobaccodust are produced. It is known that such tobacco fines and dust can becombined with a binder to form a coherent sheet, which resembles leaftobacco and which is commonly referred to as reconstituted tobacco. Onemethod for making reconstituted tobacco of this general character isdisclosed in United States Patent 2,734,510 wherein the tobacco finesand dust are applied to a binder made of carboxymethyl cellulose,carboxymethyl hydroxyethyl cellulose or :a suitable salt thereof. Thebinder, in such compositions, ranges from about to about 50% of theweight of the tobacco employed. United States Patent 2,708,175 describesa binder for reconstituted tobacco which consists of a plant gum,principally of galactomannan. United States Patent 2,592,554 toFrankenburg describes :as binders for reconstituted tobacco variouswater-soluble polysaccharides, such as al inic and pectinic acids andtheir sodium and potassium salts, derived from plants other thantobacco. However, the addition of cellulosic binders further increasesthe amount of celluice entitled Smoking Compositions and Method ofPreparing Same, is a continuation-in-part of application, Ser. No.336,009, filed on Jan. 6, 1964, now abandoned, and makes possible theproduction of improved reconstituted tobacco sheet by a method which issimpler and more effective than the methods previously employed. Such amethod does not require refining of the binder and is, therefore, moreeasily and emciently employed than other methods for making binders andfor making reconstituted tobacco. The reconstituted tobacco which isobtained in accordance with that invention need not contain anyadditional cellulose or protein foreign to tobacco, since the binderwhich is employed may be derived solely from tobacco, and contains nomaterials other than those which naturally occur in tobacco. Thus,reconstituted tobacco produced in accordance with that invention an beso formulated as to be similar in physical properties and chemicalcomposition to natural tobacco.

The term pectic substances,- as used herein, will mean those substanceswhich are found in many plant products, and which consist essentially ofpartially methylated galacturonic acids joined in long chains.

The pectin substances found in tobacco plants contain 'acetyl groups anddiffer considerably from commercially available pectins found in otherplants, including sugar beet pectins and citrus and fruit pectins.Tobacco protopectins are uniquely insoluble in hot water as comparedwith protopectins from many other sources and comprise mainlywater-insoluble pectins (protopectins) consisting of the calcium andmagnesium salts of partially esterified and slightly acetylated polymersof galacturonic acid. The divalent calcium and/ or magnesium atoms actas crosslinks between acid chains, thus making the polymerswater-insoluble. As an illustration, the structure of the calcium saltof a polymer of galacturonic acid can be represented as follows:

losic material in the product and tends to create an acrid and bittersmoke when the product is used to make cigarettes. The naturalhydrophiiic colloid gums such as guar, locust bean, algin and othercommonly used material, such as Irish moss, have additionaldisadvantages. These materials contain proteins and other materials notfound in tobacco which add distinctive flavors of their own to tobaccoproducts during smoking. Thus, Frank'enburg, in describing the use ofvarious watersoluble polysaccharides derived from plants other thantobacco, teaches that care should be exercised that they must be in astate of refinement. Frankenbur-g teaches that these materials should befree :of extraneous matter containing compounds of nitrogen,particularly proteins, and compounds of sulfur, phosphorus and thehalogens; i.e. compounds giving undesirable products of combustion ordry distillation. Such refining is often a very tedious and diflicultoperation.

The invention set forth in copending application, Ser. No. 557,903 filedof even date herewith and now Patent 3,353,541 in the names of thepresent inventors and Although pectins have long been known asconstituents of plant tissue, it has been found extremely difhcult toseparate pectins from the remainder of plant compositions and to obtainthem as homogeneous compositions. The recovery of pectins from tobaccois even more difficult than the recovery of pectins from other plants.

In accordance with theinvention set forth in said Patent No. 3,353,541tobacco parts are bonded together by tobacco pectins which are speciallyprepared by a process which yields these pectins in a form in which theycan be employed as binder materials. The process for preparing tobaccopectins comprises first reacting tobacco parts, preferably in a form inwhich they present a large surface area, with an aqueous solution of anon-toxic reagent which is capable of reacting with and destroying thecalcium and magnesium cross-links in the pectinaceous substances whichnaturally occur in tobacco. By destroying the calcium and magnesiumcross-links, the tobacco 1 No'rE. Unless otherwise specified, the termpoetins will, tor convenience, hereinafter be employed interchangeablywith the term pectic substances.

pectins are liberated and are available for use as a binder. The tobaccopectins are then dissolved or dispersed in solution, or are at leastsufiiciently released from the inerstices of the tobacco mass so thatthey form a coating on the surface thereof. Tobacco pectins which aredissolved or dispersed are thereafter precipitated or deposited from thesolution, so that they become available for use as a binder material. Inthis way, the tobacco parts can be bonded together without introducingany materials as binders which are foreign to the tobacco, and withoutthe need for the purification of th tobacco pectins, inasmuch as anyimpurities present are normally present in tobacco and, thus, do not addany undesired qualities to the tobacco.

The tobacco parts which can be employed include tobacco leaves, stemsand stalks, or a mixture of these, whether in sheet, flake orparticulate form. Preferably, the parts are ground, cut or otherwiseprepared in a form which presents a large surface area. The portions ofthe plant comprising the stems or midribs, and often referred to astobacco petioles, are the preferred starting materials. Tobacco stalkscontain lesser amounts of pectinaceous materials but can also beemployed.

In the first step of the process set forth in said Patent 3,353,541,tobacco pectins are liberated from pectinaceous materials in tobacco byreacting the pectinaceous materials with a reagent which is reactivewith the calcium (and/ or magnesium) contained in them to form acompound or product having a lower calcium ion, and, in the case ofmagnesium, magnesium ion, concentration in the treating solution thanthe naturally occurring calcium (or magnesium) pectate.

The reaction may be generally represented by Equation I, whichillustrates the reaction of one type of tobacco protopectin (a calciumsalt of a polymer of galacturonic acid) wherein calcium cross-links arepresent with the reagent of the present invention. In the equation, Rmay be hydrogen, in which case the product is pectic acid, or R may be amonovalent inorganic cation, such as sodium, potassium or ammonium.

Equation I tln'oss-link (I7OOCa T e f 1r II H O-CH H H H-CO--C H HC- ZRTreating re- CC G- agent of this 2) I invention.

11 on ooocI-n Calcium Poet-ate C O O R CHaCO O (|)H AI O C\ -/O a H-O-C-H H H HCOC H H H/-G-O- ZCa Product having (3 0 C0 lower cation conl(g I centration than OH H COOCH; the calcium peetate in the treat ingsolution.

A particularly preferred reagent for use in accordance with thatinvention, functions partially as a sequestering agent, and partially asa precipitating reagent. Such a reagent is DAP (diammoniurn monohydrogenorthophosphate).

Once the tobacco pectins have been liberated from the tobacco, by theremoval of the calcium and magnesium cross-links, due to their chemicalreaction with the DAP, the pectins should be released from theinterstices of the tobacco. That is, they will be made available to thesolution or suspension or, in certain instances, they By concentrationis meant concentration or activity as set forth in Glasstoue. Textbookof Physical Chemistry, 2nd edition, page 954, D. V. Nostrand Company,Inc.

4 will be merely deposited on the surface of the tobacco particles. Thisrelease may be accomplished concurrently with the first step by reactingwith the solution of the DAP treating reagent.

In accordance with the next step of the process, the liberated andseparated tobacco pectins can next be precipitated from the treatingsolution.

The tobacco pectins can be recovered by concentrating the solution orsuspension in which they are present until they precipitate. Thisprecipitate might also be characterized as an intractable mass, sinc thepectin solution, upon concentration, generally becomes progressivelymore viscous until it finally dries to leave a deposit in a glassy solidstate.

While the tobacco pectins can be separated and purified before use, theyare preferably employed just as they are produced, i.e. in combinationwith the treated tobacco plant parts from which they were obtained. Byusing them in this state, no original tobacco flavors are lost and noexpensive refining operations are required.

Although it is not necessary, the thixotropic properties of solutionscontaining soluble pectins can be adjusted in the preparation of a curedsheet by the addition of such materials as calcium chloride. If anycomplex or precipitate formed in the first step of this process ispresent with the soluble pectates, the thixotropic properties of themixture can also be adjusted by adjusting the pH to precipitate calciumand magnesium pectates.

The term tobacco pectins as used throughout this specification meansliberated tobacco pectins and comprehends pectins which have been freedor liberated from tobacco and are, therefore, not bound into the tobaccostructure, as differentiated from the insoluble, naturallyoccurringprotopectins which are bound into a plant cell structure. The termincludes the free pectinic or pectic acid, as well as soluble salts suchas the sodium, potassium, ammonium, pectates and pectinates, andinsoluble salts such as the calcium and magnesium pectates andpectinates depending on what method is employed to liberate and obtainthem from the naturally-occurring insoluble protopectins.

The tobacco pectins produced or liberated in situ or isolated by meansof the invention set forth in said Patent No. 3,353,541 can be used asthe sole binder material for reconstituted tobacco, i.e. no othermaterials need be added to make the sheet. They can be sprayed, extrudedor cast, thus facilitating application onto a moving belt carryingtobacco dust. Under proper conditions of formulation and processing,reconstituted tobacco made with the tobacco pectins produced by theinvention exhibit excellent physical and aromatic properties. Theultimate tensile and wet strengths of the reconstituted tobacco aregood. While no other materials need be added to the pectinaceous binderother materials can be added, if desired. For example, organic acids andpreservatives which may in themselves be of tobacco origin may be added.Plasticizers, such as glycols and polyglycols, and humectants, such asglycerin, may also be added, if desired. In addition, the gel strengthof the tobacco pectins can be regulated by partial precipitation tocontrol such rheological properties as viscosity, fluidity andelasticity. Other additives or dispersants may be added in small amountsto regulate slurrying qualities, provided, however, that such substancesare not added in large enough quantities to adversely affect the flavoror aroma of the final product. Furthermore, the tobacco pectins can becombined with water-soluble gums or water-dispersible gums commonly usedas binders for tobacco sheets such as methyl cellulose, sodiumcarboxymethyl cellulose, guar gum, locust bean gum, or alginates,although it is preferred to minimize or eliminate such additions inorder to obtain a product which most closely resembles natural tobacco.

The product from treating the tobacco plant parts in accordance with themethods of the process of said Patent No. 3,353,541 may be cast directlyand dried and cut into particulate material similar in physical form toordinary smoking tobacco and so used, preferably mixed with tobacco leafcut or shreaded in the usual manner. The product may be cast in sheetform, in blocks or as threads or other shapes, as desired. An importantuse, however, of the prepared composite slurry or easily molded isolatedpectinaceous mass is as a binder for ground tobacco and for the makingof corresponding tobacco products suitable for smoking. Sheet materialof widely different properties may be formed by suitable variations inthe manner of forming. One method and product comprises flowing thecomposite slurry onto a moving belt and applying a layer of dry groundor fragmented tobacco to the wet adhesive surface. If desired, there maybe first applied to the belt a layer of the tobacco, followed by a layerof the binder, and then a top layer of the tobacco. Various additivesmay be included with the ground tobacco such as flavo'rants,plasticizers and aromatic substances. The web is ultimately dried andthen suitably moistened and rolled up. Such methods of formingcontinuous sheets are known generally in the art and the details neednot be further described. Representative of this procedure is theapparatus and method disclosed in US. Patent 2,734,513.

Another method of forming a reconstituted tobacco product, with theslurry of the isolated tobacco pectins as a binder, comprises mixingground tobacco thoroughly therewith into a mass of dough-likeconsistency and then casting the mass in sheet form onto a moving beltsurface followed by drying and remoistening in accordance with knownprocedures. Representative of this procedure is the apparatus and methoddisclosed in US. Patents 2,708,175 and 2,769,734. Obviously, thereconstituted tobacco may also be formed by molding or other suitablemeans.

A particularly preferred aspect comprises employing, as a binder ordirectly, the mixture of tobacco and tobacco pectins which have beenproduced in situ, without any separation steps and without the necessityfor any aditional adhesive materials.

I have observed that, when reconstituted tobacco sheets are made usingDAP under the conditions set forth in said Patent No. 3,353,541, the DAPwhich is employed can have varying effects on the resulting sheet. Thus,when more than about 5% by weight of DAP (based on the weight oftobacco) is used, under the circumstances set forth in said application,the resulting binder or cast sheet may have some qualities that are notcompletely satisfactory. For example, when more than about 5% by weightof DAP is employed the cast may be somewhat darker than might be desiredor might burn less evenly than sheets produced using less than 5% ofDAP.

I have discovered a means to improve the burning characteristics ofreconstituted tobacco sheets and particularly those made employing morethan 5% by weight of DAP and to greatly lower the viscosity of solutionemployed in making such sheets to the point where the resulting sheetsare much more satisfactory from an engineering aspect.

Essentially, the present invention comprises a process by which analkaline earth metal phosphate is added to the DAP treated slurry beforeit is cast directly on a belt.

The alkaline earth metal phosphate may be a calcium phosphate or amagnesium phosphate and may be a synthetic phosphate or a mixture ofsynthetic prosphates or may be in the form of a naturally-occurringphosphate. Examples of suitable phosphates include: dicalcium phosphate,calcium metaphosphate, monocalcium phosphate as salts of phosphoricacid, calcium pyrophosphate, tricalcium phosphate, monetite, brushite,martinite, isoclasite, fluorapatite, chloroapa'tite, podolite, dahllite,trancolite, tribasic or normal magnesium phosphate, magnesium acidphosphate, biphosphate, magnesium pyrophosphate, magnesium ammoniumphosphate and the like. The types of phosphates and the states in whichthey may be employed are varied. For a detailed description of calciumand magnesium phosphates of the type which may be used, see J. R. VanWazer, Phosphorus and Its Compounds, vol. I, Interscience, New York,1958, pages 523542.

The best ash formation and subjective smoking qualities of tobaccoproducts produced from such a process are obtained when the resultingsheet contains from about 13 to 20% of the alkaline earth metalphosphate (by weight) on a solids basis, although from 1 to 50% byweight on a solids basis, of the phosphate, based on the total weight ofthe reconstituted tobacco sheet, can be employed with good results.

The sheet in a preferred embodiment should be made using from 1 to 50%by weight (based on the total sheet) of DAP in combination with from 1to 50% by weight alkaline earth metal phosphates. However, the alkalineearth metal phosphate may also be used to improve sheets made by any ofthe known methods for making reconstituted tobacco sheets, for example,those methods set forth in Patent No. 3,353,541.

The alkaline earth metal phospate may be added to the tobacco parts,while in slurry form, either with or without other ingredients, beforethe slurry is cast as a sheet.

I have found that such phosphates, as exemplified by calcium phosphate,contrary to what would be expected, lowered the viscosity of theslurries to which they were added. For example, calcium phosphatelowered the viscosity of a slurry of tobacco particles and DAP fromabout 17,000 centipoise to about 9,000 centipoise. The smokingcomposition made when the slurry was cast on the belt burned evenlyyielding a firm gray ash and gave a subjectively acceptable smoke.

The following examples are illustrative:

Example 1 One hundred grams of whole bright stems were covered with 1500milliliters of hot tap water. To the mixture was added 7.5 grams ofdiammonium monohydrogen orthophosphate. Sufiicient ammonium hydroxidewas added to bring the pH to 7.0. The resulting mixture was kept over aboiling water bath for three hours. A weighed sample was dried in a C.Freas force draft oven to constant weight. The dry weight was divided bythe original weight to determine percent solids. Total solids were foundto be 6.61%. The slurry was filtered and proportional amounts of thefiltrate and the filtered cake were then remixed for use as a binderbase. Three hundred grams of the binder were mixed with 5.949 grams ofcalcium phosphate, NF (30% of the total solids). A like amount of thebinder base to which no calcium phosphate was added was prepared for useas a control. After thorough mixing, the two sets of binder materialwere cast on metal plates in sheets 50 mils thick. The sheets were thensteam dried. It was observed that the binder containing the calciumphosphate was much lighter in color than the control, a quality to bedesired in a smoking composition. 'I\ vo sets of the binders wereshredded into cigarette filler, made into cigarettes, and smoked. Thecontrol which had no calcium phosphate burned unevenly and produced ahard, black ash. The experimental cigarettes with the calcium phosphateburned evenly, produced a gray ash which was slightly weak and gave afairly mild smoke which was less hard than that of the control.

Example 2 One hundred grams of bright tobacco stems were treated asdescribed in Example 1 and 300 grams of the slurry (total solids 6.61%)was used in preparing a mixture to which 3.966 grams of calciumphosphate were added (20% of total solids). The resulting material wasmixed in a Waring blendor and cast on metal plates in a sheet 50 milsthick. A similar mixture without the addition of calcium phosphate wastreated in the same manner for use as a control. The sheet containingthe calicum phosphate was lighter in color than the control. The twosets of filler were shredded and made into cigarettes. When they weresmoked, it was found that the cigarette without the calcium phosphateburned unevenly and had a hard, black ash. The experimental cigarettewith calcium phosphate burned evenly, had a strong gray ash and Wasmilder in taste than the control.

Example 3 In a pilot plant run, a slurry having a viscosity of 16, 800centipoise (Brookfieid, 20 r.p'.m.) and a solids content of 12.05% wasmade from the following materials:

Run 1 Run 2 Run 3 Avg.

Sheet weight, at 28% moisture, g./it. 20. 94 19. 83 19. 81 20.19 Dust,Loss/it. 0. 0.10 0. 10 0. l0

Moisture Cheek 23.1%,

after 1 hr. in humidity cabinet Sheet wt. dry basis 15 grams Twenty-fivepounds of calicurn phosphate (NF) was added to a second portion of theslurry prepared from the ingredients given above. This amount of calciumphosphate corresponded to 0.20 part per part of leaf dust. This wassprayed on a stainless steel belt and dried to form a sheet whichweighed about grams per square foot.

The following data was obtained for the sheet:

Run 1 Run 2 Run 3 Avg.

Sheet weight, at 25.4% Moisture,

g. ft. 13.36 13. 45 13.27 13.36 Dust, loss/ft. 0.00 0.08 0.05 0.04

Moisture check 25.4%, after 1 hr. in

humidity cabinet Sheet weight 9.97

It was noted that the addition of the calcium phosphate actually causeda reduction of Brookfield viscosity from 17,000 centipoise to about9,000 centipoise. The calcium phosphate addition also resulted in alighter colored product.

Cigarettes made from filler prepared from the two types of sheets weresmoked and the same advantages described in Examples 1 and 2 wereobserved.

I claim:

1. A method of making a reconstituted tobacco sheet which comprisesreacting at a temperature of from room temperature to about 300 F.tobacco plant parts with an aqueous solution of diammonium acidphosphate, said phosphate comprising from 1 to 30 parts by weight per100 parts of tobacco, the reaction being continued until a measurableamount of pectins are released from the tobacco, adding from 1 to partsby weight per parts of tobacco of an alkaline earth metal phosphateselected from the group consisting of calcium and magnesium phosphates,and casting the resulting material as a tobacco sheet.

2. The method of making a reconstituted tobacco as set forth in claim 1wherein said alkaline earth metal phosphate is calcium phosphate.

3. The method of making a reconstituted tobacco as set forth in claim 1wherein said alkaline earth metal phosphate is magnesium phosphate.

References Cited UNITED STATES PATENTS 2,613,673 10/1952 Sartoretto eta1 131-17 3,012,915 12/1961 Howard 131-17 3,121,433 2/1964 Plunkett eta1 13117 SAMUEL KOREN, Primary Examiner.

MELVIN D. REIN, Examiner.

1. A METHOD OF MAKING A RECONSTITUTED TOBACCO SHEET WHICH COMPRISESREACTING AT A TEMPERATURE OF FROM ROOM TEMPERATURE TO ABOUT 300*F.TOBACCO PLANT PARTS WITH AN AQUEOUS SOLUTION OF DIAMMONIUM ACIDPHOSPHATE, SAID PHOSPHATE COMPRISING FROM 1 TO 30 PARTS BY WEIGHT PER100 PARTS OF TOBACCO, THE REACTION BEING CONTINUED UNTIL A MEASURABLEAMOUNT OF PECTINS ARE RELEASED FROM THE TOBACCO, ADDING FROM 1 TO 50PARTS BY WEIGHT PER 100 PARTS OF TOBACCO OF AN ALKALINE EARTH METALPHOSPHATE SELECTED FROM THE GROUP CONSISTING OF CALCIUM AND MAGNESIUMPHOSPHATES, AND CASTING THE RESULTING MATERIAL AS A TOBACCO SHEET.